The company said it planned to offer employees 150 percent of a pilot's hourly wage to work those holidays, according to the Dallas Morning News.

But the pilots union filed a grievance, saying the company violated the labor contract. The union wanted input on how to fix the issue.

"This is certainly not routine," Tajer told the Morning News at the time. "This is a crisis right now, and in that crisis, they've gone solo."

Earlier this year, Ryanair, a budget airline in Ireland, canceled close to 2,000 flights in September so its staff could take a vacation, leaving thousands of passengers without flights for their holidays.

Meanwhile, Delta announced this week that the company flew 23,000 flights for 2.35 million customers without a single cancellation during the Thanksgiving holiday. The flights ran from Wednesday to Sunday, with an on-time rate of 92.7 percent.

A successful weekend added to the 11-day streak for Delta without a cancellation for its mainline or Delta Connection regional flights. The company also has a 42-day streak on just the mainline.